A current mirror is a type of current amplifier that provides a high impedance output current proportional to an input current. The output current is typically used to drive a load for high gain. A simple current mirror generally consists of a single input and a single output transistor pair, with the gate electrodes of the pair being tied together and to an input voltage node at the drain of the input transistor. The sources of the transistors are connected to a reference voltage node that is common to both transistors. The drain and gate of the input transistor are connected to a current source that provides a quiescent reference current. Because the input and output transistors have their gates and sources tied together, a corresponding output current arises in the conduction path of the output transistor. Generally, the input and output transistors are identical and there is a substantially unity gain in the current. Such current mirrors are commonly used to provide active loads in high gain amplifier stages.